Torque-transmitting device

ABSTRACT

An electromagnetic torque-transmitting device or coupling includes a housing for enclosing a drum which extends around and is magnetically coupled with a rotor. The housing defines a chamber which is pressurized with a suitable cooling medium, such as air, which flows around the coupling to cool it during a transmission of torque between the drum and rotor. The pressurized cooling air flows into pockets spaced around the drum and impinges against the drum at circumferentially spaced locations around the drum while passing under a baffle to an exhaust pocket. The cooling air is then exhausted to the atmosphere through conveniently located openings. A plurality of circumferentially extending grooves are formed in an outer wall of the drum to further promote a transfer of heat from the drum to the cooling air.

United States Patent Moyer 1 Feb.8, 1972 [54] TORQUE-TRANSMITTING DEVICE [72] Inventor: William H. Moyer, Kenosha, Wis.

[73] Assignee: Eaton Yale & Towne Inc., Cleveland, Ohio [22] Filed: Sept. 4, 1970 211 App]. No.: 69,702

[52] US. Cl. .310/105 Primary Examiner-D. X. Sliney Attamey-Yount and Tarolli ABSTRACT An electromagnetic torque-transmitting device or coupling includes a housing for enclosing a drum which extends around and is magnetically coupled with a rotor. The housing defines a chamber which is pressurized with a suitable cooling medium, such as air, which flows around the coupling to cool it during a transmission of torque between the drum and rotor. The pressurized cooling air flows into pockets spaced around the drum and impinges against the drum at circumferenu'ally spaced locations around the drum while passing under a baffle to an exhaust pocket; The cooling air is then exhausted to the atmosphere through conveniently located openings. A plurality of circumferentially extending grooves are formed in an outer wall of the drum to further promote a transfer of heat from the drum to the cooling air.

18 cums, s nnwin Figures PAIENTEB FEB 8 m2 SHEET 1 OF 2 FIG I 5y ATTORNEYS PATENTEUFEB 8 1912 SHEET 2 UF 2 //VVE/VTOR W/LL/AM H. MOYER FIG .5

ATTORNEYS TORQUE-TRANSMITTING DEVICE The present invention relates to a torque-transmitting device, and more particularly to a cooling system for cooling an electromagnetic coupling which interconnects driving and driven members. It is well recognized in the art that the term coupling includes clutches, brakes, dynamometers and the like.

A known electromagnetic coupling includes a rotor which is disposed within a rotatable drum. A coil is energized to generate a magnetic field which magnetically interconnects the rotor and drum so that torque can be transmitted between them. The passage of this magnetic field through the rotor and drum results in the generation of heat while torque is being transmitted therebetween. The dissipation of this heat has been a constant problem and many efforts have been made to effectively dissipate the heat. In some known electromagnetic couplings, heat dissipating fins are provided which extend from the exterior of the drum. However, these fins are difficult to form and may create such a loud noise that a silencer is required. Moreover, the fins also do not provide the most effective cooling of the coupling. Furthermore, grooved drums have been provided and US. Pat. No. 2,345,850 illustrates an example of such. However, all efforts to date have not been completely satisfactory.

The present invention provides an extremely effective cooling system for a torque-transmitting device and which is free of many of the prior art problems. In particular, the present system utilizes air which is pressurized so as to have a relatively high density as a cooling medium. The pressurized air is provided by a blower which is associated with the coupling and directs air into a housing for the coupling. The pressurized air provides the necessary energy to cause the air velocity to increase as it passes from an inlet air pocket, under a baffie, and to an exhaust pocket. This increase in velocity improves the heat transfer coefficient between the air and a surface to be cooled thereby. The result is an effective dissipation of the heat which is generated by the transmission of torque between the input and output members. As the inductor drum rotates centrifugal force causes the air to leave the drum. In order to supply adequate cooling fluid sufficient pressure must be furnished to, overcome the centrifugal velocity pressure. At higher drum speeds cooling fluid pressure must be increased proportionately. For example, the inductor drum is capable of dissipating l thermal horsepower in free air and eighty thermal horsepower pressurized. Tests have been made that indicate an improvement is made in the capacity of the air to dissipate heat when the pressure and density are increased.

Moreover, the torque-transmitting device of the present invention minimizes the use of cooling fins and, yet, maintains a relatively large surface area for heat transfer through the provision of a grooved drum forming one of the input or output members. These grooves are readily machined in the drum as opposed to the difiiculties heretofore encountered in forming fins on the drum.

Furthermore, the cooling medium is distributed in spaced circumferential pockets around the input and output members and exhaust openings are located adjacent to these pockets. The pockets are disposed so that a given point on one of the members sequentially passes the pockets and is exposed to the cooling medium therein and the exhaust openings. This total cooling system, which includes the high density air, the grooved drum, spaced pockets, and exhaust openings, is highly effective. Tests have indicated substantial increases in cooling effectiveness as compared to known couplings which do not incorporate all of these features.

Accordingly, it is an object of this invention to provide a new and improved torque-transmitting device which is effectively cooled by the transfer of a relatively large quantity of heat to a cooling medium and which operates without creating an excessive amount of noise and is readily manufactured.

Another object of this invention is to provide a new and improved torque-transmitting device having a means for effecting the transmission of torque between input and output members in a manner which tends to generate heat as torque is transmitted and wherein cooling fluid is directed under pressure into a housing for the members and into a heat-transferring relationship with the input and output members to at least partially dissipate heat generated during the transmission of torque between the input and output members.

Still another object of the present invention is to provide a new and improved torque-transmitting device, as set forth in the next preceding object, wherein the housing includes a plurality of baffles which cause the cooling fluid to impinge against at least one of the members at a plurality of circumferentially spaced locations before being exhausted through a plurality of openings in the housing.

Another object of this invention is to provide a new and improved torque-transmitting device having a housing forming a chamber for enclosing rotatable input and output members and wherein the housing defines a plurality of pockets and exhaust openings disposed in such an arrangement that a grooved surface of one of the members is sequentially subjected to a cooling medium in the pockets as the grooved surface rotates past the pockets.

These and other objects and features of the present invention will become more apparent upon a consideration of the following description taken in connection with the accompanying drawings wherein:

FIG. 1 is a sectional view of a torque-transmitting device constructed in accordance with the present invention and illustrating the relationship between a rotatable drum or input member of a coupling assembly and an associated housing;

FIG. 2 is a fragmentary sectional view, taken generally along the line 2-2 of FIG. 1, and further illustrating the relationship between one of the grooves formed in the drum of the coupling and the housing; and

FIG. 3 is a plan view, taken generally along the line 3-3 of FIG. 1, illustrating the relationship between a plurality of outlets forrned in the housing and the drum.

The present invention provides a torque-transmitting device 10 for transmitting torque from an input shaft 12 which is driven from a suitable source of power to an output shaft 14 which is connected with a driven machine or assembly. However, it should be understood that the shaft 14 could be driven to transmit torque to the shaft 12. The torque-transmitting assembly 10 includes a coupling 18 which is located within a generally cylindrical housing 20. The coupling 18 is of a known electromagnetic type and includes a rotor or output member 24 which is disposed within a cylindrical work chamber 26 in a drum or input member 28. A plurality of coils 32 mounted on poles of the rotor 24 are energizable to generate a magnetic field which extends from the rotor 24 into the drum 28 to magnetically couple the rotor 24 and the drum 28. However, it should be understood that the coils 32 could be mounted in a stationary relationship with the housing 20.

When the coils 32 are energized, rotation of the input shaft 12 is transmitted by the drum 28 and rotor 24 to the output shaft 14. Lines of flux for the energized coils 32 extend across a cylindrical air gap 40 between the rotor 24 and drum 28 to magnetically interconnect them so that rotation of the drum is transmitted to the rotor. The drum 28 is fixedly connected by a key 41 to the input shaft 12 and the rotor 24 is keyed at 42 to the output shaft 14.

As the torque load on the output shaft 14 increases, some slippage will occur between the rotor 24 and drum 28. To accommodate this slippage, the rotor 24 is supported by bearings 44 so that relative rotation can occur between the drum and rotor while both of them are rotating relative to the housing 20. As slippage occurs between the drum 28 and rotor 24, the drum is heated in a known manner under the influence of induced currents within the drum.

The present invention is directed to an improved system for effectively dissipating the aforementioned heat which is generated by torque transmission. In this connection, a plurality of grooves 48 are formed in the drum 28 to increase the surface area of the drum and promote the transfer of heat to a cooling medium which contacts the drum. The annular grooves 48 are formed in a cylindrical wall 50 of the drum 28 and are concentric with the axis of rotation of the drum and the shafts l2 and 14. The grooves 48 being concentric with the axis of the drum, can be readily formed by known manufacturing techniques including machining.

The cooling of the drum 28 is effected by the flow of a cooling medium over surfaces thereof and, specifically, by the flow of a cooling medium through the grooves 48 therein. While many different known types of cooling mediums could be used for this purpose, in the illustrated embodiment of the invention, air is utilized as the cooling medium.

While the coupling 18 can be cooled by admitting air at atmospheric pressure into the housing through suitable openings, the coupling 18 is most effectively cooled by pressurizing a chamber 54 within the housing 20. This increases the density of the air and promotes a flow of the air around baffle plates 56 of a manifold arrangement 58 and into the grooves 48 wherein the air is heated to cool the drum 28. This heated air then flows out of the housing through rectangular openings 60 disposed at spaced apart locations along a cylindrical wall 62 of the housing (see FIGS. 2 and 3). Cooperation between the baffle plates 56 and the rotating drum 28 further induces a flow of air from manifold chambers 66 into the grooves 48 and from there through the openings 60.

During operation of the torque-transmitting device 10, air under pressure is conducted into the chamber 54 through an inlet duct 70 which extends'between the housing 20 and a suitable blower or other compressor (not shown). A plurality of movable louvers or slats 72 are provided in the duct 70 immediately adjacent to an opening 74 (FIG. 1) in the housing 20 to facilitate controlling the flow of air through the opening in a known manner. While the use of an external compressor or blower is preferred, since its output is independent of the speed of operation of the torque-transmitting device 10, it is contemplated that a blower or compressor could be provided as part of the input or output member, within the housing 20.

Once the relatively high pressure cooling air enters the chamber 54, it tends to flow outwardly into the longitudinally extending manifold chambers or pockets 66 (FIGS. 2 and 3) formed at circumferentially spaced locations around the drum 28. The baffle plates 56 and pockets 66 extend lengthwise of the housing 20 between circular end walls 76 and 78 of the housing. Therefore, as the drum 28 rotates, it is sequentially exposed to the relatively dense, pressurized cooling air in each of the pockets 66 in turn.

After the air has moved in a generally axial direction along the manifold chambers or pockets 66, the air flows inwardly around inner ends or edges 80 of the baffle plates 56 into the grooves 48. As the air flows inwardly, it impinges against the grooved surface of the drum 28. The direction of flow of the air then changes so that it moves circumferentially around the drum 28 in the manner indicated schematically by the arrows in FIGS. 2 and 3. It is believed that as the air flows inwardly around the inner edges 80 of the baffle plates 56, the air tends to be packed or compressed into the grooves 48 under the influence of both the relatively high pressure in the pockets 66 and the drum 28 which is rotating at a relatively high speed past the stationary baffle plates.

Once the air has entered into the grooves 48, there is intimate contact between the air and the relatively large surface area of the annular rings 84 (FIG. 1), which extend radially outwardly from the annular wall 50. This contact over a relatively large surface area promotes the transfer of heat from the drum 28 to the air in the grooves 48. While the relatively large surface area provided by the rings 84 and grooves 48 promote the transfer of heat, it is contemplated that rings 84 may be omitted in certain torque-transmitting devices which can be adequately cooled by a flow of pressurized air into engagement with a smooth surfaced drum.

After heat has been transferred to the pressurized air from the drum 28;, the heated air enters exhaust pockets 88 circumferentially located around the drum 28 and in between the inlet pockets 66. The heated air is exhausted to the atmosphere through either outlets 60 (H68. 2 and 3) at the outer wall 62 of the housing 20, or by connecting the exhaust pockets 88 to a common exhaust chamber and thence to the atmosphere through conveniently located openings in the housing '20..This results in a point on the external surface of the drum 28 being exposed to the relatively cool, pressurized air in the pockets 66 and then to the outlets 88 through which the heated air is exhausted. It is believed that this alternating exposure of the surface of the drum 28 to the pockets 66 of cooling air and to the outlets 88 contributes to the effective cooling of the drum.

The drum 28 cooperates with the baffle plates 56 to define therebetween aplurality of relatively small elongated openings (see FIG. 1) which extend parallel to the axis of rotation of the drum. These openings 90 have inwardly projecting teeth or fingers formed by the grooves 48. To facilitate pressurizing the chamber 54, the combined area of all of the openings 90 formed between the inner edges of the baffle plates 56 and the drum 28 is less than the cross-sectional area of the opening 74 in the duct 70. Therefore, the chamber 54 can be readily pressurized to a desired level by a flow of air under pressure from a fan or blower. Pressurizing the chamber 54 advantageously promotes a flow of air through the openings to the atmosphere which is at a somewhat lower pressure.

In addition to promoting a flow of air around the drum 28, pressurizing the chamber 54 results in a flow of air around the rotor 24 to further cool the coupling 18. Thus, the rotor 24 has a plurality of openings, indicated generally at 94 in FlG. 1, through which air flows in a generally axial direction, as indicated by the arrows in FIG. 1. Of course, this flow of air cools the rotor 24. The air heated by the rotor 24 then flows through openings 98 in a circular end wall 100 of the drum 28. The heated air then flows around the end baffle plates 104 and the axially extending baffle plates 56 to the outlet 88 with the air from the grooves 48 in the drum. This flow of air around the rotor 24 is promoted by fins 108 which extend outwardly from the end wall 100 of the drum 28. The fins 108 may be eliminated with the use of external blowers or may be used in an internal blower with air entering from an opening through wall 76 (not shown). This would necessitate a reversing of the direction of air flow through the coupling. However, cooling the drum with pressurized air would still be effected.

The cooperation between the grooves 48 and the circumferentially spaced outlets 88 enables the drum 28 to be effectively cooled without generating a relatively high level of noise. In fact, the flow of air through the grooves and around the baffle plates 56 is so quiet that it is not necessary to use a silencer as heretofore utilized with certain types of couplings having fins connected to their outer surface to promote cooling. it is believed that this relatively quiet operation of the torque-transmitting device 10 may be due to a relatively smooth flow of air through the grooves 48.

Moreover, it has been determined during tests that the combined effect of providing the grooves 48 in the exterior of the drum 28 and pressurizing the chamber 54 results in the cooling effect on the coupling 18 being approximately four times greater than the cooling effect on a similar coupling which did not have the grooves and was not associated with a pressurized housing. It is theorized that this greatly increased heat transfer is at least partially due to the increased velocity of the cooling air as it comes in intimate contact, at numerous locations, with the external rotating surface of the drum. The addition of grooves increases the area of contact with the drum and provides a restricted passage for the cooling air. While this explanation of the increased cooling effect obtained from the pressurizing of the chamber 54 and from the grooves 48 is believed to be correct, the explanation of the improved cooling effect is merely to assist in understanding the invention and the invention is not intended to be limited to any particular theory of operation of the coupling 18. It should also be understood that, although the greatest increase in cooling effect over a smooth surfaced drum is obtained by the combination of the provision of the grooves 48 and pressurizing the chamber 54, an increase in the cooling effect over the smooth surfaced drum can be obtained by pressurizing the chamber 54 without providing the grooves 48 in the surface of the drum.

From the foregoing description, it can be seen that the torque-transmitting device includes an electromagnetic coupling 18 having a drum 28 and a rotor 24 which tend to become heated as torque is transmitted from the input shaft 12 to the output shaft 14. The drum 28 has a plurality of rings 84 which define circumferentially extending grooves 48 in the outer surface of the drum. The coupling 18 is enclosed by a housing 20 having baffle plates 56 which form circumferentially spaced pockets 66 to which the surface of the drum 28 is sequentially exposed as it rotates. Heat is transferred at a relatively high rate from the surface of the grooved drum 28 to the relatively dense cooling air. This heated air is exhausted through the openings 60 with a minimum of noise to at least partially dissipate the heat generated upon the transfer of torque between the drum 28 and rotor 24. It should be noted that, although air is utilized as the cooling medium in the illustrated embodiment of the invention, it is contemplated that in different environments other fluids will be utilized as a cooling medium and, in certain environments, the cooling medium may even take the form of a liquid.

Furthermore, although a salient pole-type coupling 18 has been illustrated herein, it should be understood that the present invention can be used with other types of couplings. Specifically, the coupling could be of the well-known stationary field eddy current type. Moreover, while the present invention has been disclosed as being utilized in an electromagnetic coupling, it should be appreciated that the concept of the present invention is equally applicable to dynamometers and electromagnetic brakes. Also the pole configuration could be of the interdigited type. A coupling of this type is illustrated in US. Pat. No. 3,217,197 and the present invention may be applied thereto. The interaction between a grooved drum of any of these and other known types of couplings with the pressurized air in a housing, similar to the housing 20, would be substantially the same and would result in improved cooling of the coupling.

What is claimed is:

1. A torque-transmitting device comprising a first member, a second member rotatable relative to said first member, means for effecting the transmission of torque between said first and second members in a manner which generates heat as torque is transmitted therebetween, housing means enclosing said first and second members and defining a chamber for receiving a cooling medium for dissipating at least in part the heat generated by the transmission of torque between the first and second members, outlet means disposed in said housing means for providing an egress for said cooling medium from said housing means, said second member establishing a cen trifugal force which acts to direct the cooling medium away from said second member upon rotation of said second member relative to said first member, and means for providing a flow of cooling medium into said housing means under a pressure which is greater than the pressure effected by said centrifugal force established by said second member acting on the cooling medium to enable the cooling medium to move against said centrifugal force into a heat-transferring relationship with said first and second members whereby the pressurized cooling medium effects efficient transfer of heat from said members.

2. A torque-transmitting device as set forth in claim 1 wherein said housing means includes baffie means which cooperates with one of said members to cause the cooling medium to impinge against said one member at a plurality of circumferentially spaced locations.

3. A torque-transmitting device as set forth in claim 2 wherein said one member has an outer surface defining a plurality of grooves which extend in a direction transverse to the axis of rotation of said one member to receive the cooling medium and facilitate a transfer of heat to the cooling medi- 4. A torque-transmitting device as set forth in claim 3 wherein said baffle means includes a plurality of walls each of which extends axially of said one member and has an inner end portion which is disposed adjacent to and cooperates with said grooves in said one member to at least partially define a passage through which at least a portion of the cooling medium flows prior to entering said grooves.

5. A torque-transmitting device as set forth in claim 3 wherein said housing means includes an inlet means through which the cooling medium enters the chamber, said baffle means including a plurality of walls which extend along said one member in a direction transverse to the longitudinalaxis of said grooves and cooperate with said grooves to define a plurality of passages through which the cooling medium passes in flowing from said inlet means to said outlet means.

6. A torque-transmitting device as set forth in claim 3 wherein said grooves have a generally annular configuration and are disposed in a coaxial relationship with said one member.

7. A torque-transmitting device as set forth in claim 1 wherein said means for effecting the transmission of torque between said first and second members includes a coil for generating an electromagnetic field which extends between said first and second members.

8. A torque-transmitting device as set forth in claim 1 wherein said housing means at least partially defines inlet means through which the cooling medium flows under pressure into said chamber and said outlet means defines a plurality of openings at circumferentially spaced locations adjacent one of said members and through which the cooling medium flows from said chamber, said openings having a combined cross-sectional area which is at least slightly smaller than a total open cross-sectional area defined by said inlet means so that fluid is held under pressure in said chamber.

9. A torque-transmitting device as set forth in claim 1 wherein said housing means includes an outer wall having a plurality of openings therein at spaced apart locations which cooperate to form said outlet means, a plurality of baffle plates extending inwardly from said wall toward said members and having innermost edge portions which cooperate with an outer surface means of one of said members to at least partially define passages through which fluid can flow under pressure to said openings.

10. A torque-transmitting device as set forth in claim 9 wherein said outer surface means of said one member defines a plurality of grooves which have an annular configuration and are disposed in a coaxial relationship with said one member, at least some of said baffle plates extending longitudinally in a direction parallel to the axis of rotation of said one member.

11. A torque-transmitting device comprising relatively rotatable first and second members, means for transmitting torque between said first and said second members in a manner which generates heat, a housing for said first and second members defining a chamber for a cooling medium for dissipating the heat generated upon torque transmission between said first and second members, means in said housing defining a plurality of pockets for the cooling medium at circumferentially spaced locations around one of said members, and means defining a plurality of exhaust openings adjacent said pockets for directing cooling medium from the chamber, said one of said members having a grooved surface portion which rotates past said pockets and said exhaust openings during transmission of torque between said members, said grooved surface portion being sequentially subjected to the cooling medium in said pockets as it rotates and at least partially defining a passage for flow of fluid from said pockets to said exhaust openings.

12. A torque-transmitting device as set forth in claim 11 further including means for maintaining the cooling medium in said pockets under pressure to thereby promote a flow of the cooling medium from said pockets and through said passage to said exhaust openings.

13. A torque-transmitting device as set forth in claim 11 wherein the cooling medium is a compressible fluid and said device further includes means for pressurizing the cooling medium in said pockets to thereby increase the density of the cooling medium to which the grooved surface portion of said one member is subjected as it rotates.

14. A torque-transmitting device as set forth in claim 11 wherein said housing includes a plurality of baffles which extend inwardly toward said grooved surface portion of said one member to at least partially define said pockets.

15. A torque-transmitting device as set forth in claim 14 wherein said exhaust openings are formed in said housing at locations intermediate said baffles and said pockets at circumferentially spaced locations around said one member.

16. An electromagnetic torque-transmitting device comprising rotatable input and output members, an electrical coil associated with said input and output members and energizable to create a magnetic field traversing said members so that relative rotation of said members generates heat and effects transmission therebetween, housing means at least partially enclosing said input and output members and defining a chamber for receiving cooling medium for dissipating at least in part the heat generated by the transmission of torque between the input and output members, and means for providing a flow of the cooling medium into said housing means and providing pressurized cooling medium therein in a heat-transferring relationship with said input and output members whereby the pressurized cooling medium effects efficient transfer of heat from said members, said housing means including baffle means for directing the cooling medium to impinge against said one member at a plurality of circumferentially spaced locations.

17. A torque-transmitting device as set forth in claim 16 wherein said one member has an outer surface defining a plurality of grooves which extend in a direction transverse to the axis of rotation of said one member to receive the cooling medium and facilitate a transfer of heat to the cooling medi- 18. A torque-transmitting device as defined in claim 1 wherein said second member includes a plurality of grooves therein which extend in a direction transverse to the axis of rotation of said second member, said centrifugal force established upon rotation of said second member acting to direct said cooling medium from said grooves and tending to establish a vacuum in said grooves, said means for providing a flow of pressurized cooling medium providing said flow at a pressure which is greater than the pressure established by said centrifugal force to thereby effect the flow of the cooling medium into said grooves. 

1. A torque-transmitting device comprising a first member, a second member rotatable relative to said first member, means for effecting the transmission of torque between said first and second members in a manner which generates heat as torque is transmitted therebetween, housing means enclosing said first and second members and defining a chamber for receiving a cooling medium for dissipating at least in part the heat generated by the transmission of torque between the first and second members, outlet means disposed in said housing means for providing an egress for said cooling medium from said housing means, said second member establishing a centrifugal force which acts to direct the cooling medium away from said second member upon rotation of said second member relative to said first member, and means for providing a flow of cooling medium into said housing means under a pressure which is greater than the pressure effected by said centrifugal force established by said second member acting on the cooling medium to enable the cooling medium to move against said centrifugal force into a heat-transferring relationship with said first and second members whereby the pressurized cooling medium effects efficient transfer of heat from said members.
 2. A torque-transmitting device as set forth in claim 1 wherein said housing means includes baffle means which cooperates with one of said members to cause the cooling medium to impinge against said one member at a plurality of circumferentially spaced locations.
 3. A torque-transmitting device as set forth in claim 2 wherein said one member has an outer surface defining a plurality of grooves which extend in a direction transverse to the axis of rotation of said one member to receive the cooling medium and facilitate a transfer of heat to the cooling medium.
 4. A torque-transmitting device as set forth in claim 3 wherein said baffle means includes a plurality of walls each of which extends axially of said one member and has an inner end portion which is disposed adjacent to and cooperates with said grooves in said one member to at least partially define a passage through which at least a portion of the cooling medium flows prior to entering said grooves.
 5. A torque-transmitting device as set forth in claim 3 wherein said housing means includes an inlet means through which the cooling medium enters the chamber, said baffle means including a plurality of walls which extend along said one member in a direction transverse to the longitudinal axis of said grooves and cooperate with said grooves to define a plurality of passages through which the cooling medium passes in flowing from said inlet means to said outlet means.
 6. A torque-transmitting device as set forth in claim 3 wherein said grooves have a generally annular configuration and are disposed in a coaxial relationship with said one member.
 7. A torque-transmitting device as set forth in claim 1 wherein said means for effecting the transmission of torque between said first and second members includes a coil for generating an electromagnetic field which extends between said first anD second members.
 8. A torque-transmitting device as set forth in claim 1 wherein said housing means at least partially defines inlet means through which the cooling medium flows under pressure into said chamber and said outlet means defines a plurality of openings at circumferentially spaced locations adjacent one of said members and through which the cooling medium flows from said chamber, said openings having a combined cross-sectional area which is at least slightly smaller than a total open cross-sectional area defined by said inlet means so that fluid is held under pressure in said chamber.
 9. A torque-transmitting device as set forth in claim 1 wherein said housing means includes an outer wall having a plurality of openings therein at spaced apart locations which cooperate to form said outlet means, a plurality of baffle plates extending inwardly from said wall toward said members and having innermost edge portions which cooperate with an outer surface means of one of said members to at least partially define passages through which fluid can flow under pressure to said openings.
 10. A torque-transmitting device as set forth in claim 9 wherein said outer surface means of said one member defines a plurality of grooves which have an annular configuration and are disposed in a coaxial relationship with said one member, at least some of said baffle plates extending longitudinally in a direction parallel to the axis of rotation of said one member.
 11. A torque-transmitting device comprising relatively rotatable first and second members, means for transmitting torque between said first and said second members in a manner which generates heat, a housing for said first and second members defining a chamber for a cooling medium for dissipating the heat generated upon torque transmission between said first and second members, means in said housing defining a plurality of pockets for the cooling medium at circumferentially spaced locations around one of said members, and means defining a plurality of exhaust openings adjacent said pockets for directing cooling medium from the chamber, said one of said members having a grooved surface portion which rotates past said pockets and said exhaust openings during transmission of torque between said members, said grooved surface portion being sequentially subjected to the cooling medium in said pockets as it rotates and at least partially defining a passage for flow of fluid from said pockets to said exhaust openings.
 12. A torque-transmitting device as set forth in claim 11 further including means for maintaining the cooling medium in said pockets under pressure to thereby promote a flow of the cooling medium from said pockets and through said passage to said exhaust openings.
 13. A torque-transmitting device as set forth in claim 11 wherein the cooling medium is a compressible fluid and said device further includes means for pressurizing the cooling medium in said pockets to thereby increase the density of the cooling medium to which the grooved surface portion of said one member is subjected as it rotates.
 14. A torque-transmitting device as set forth in claim 11 wherein said housing includes a plurality of baffles which extend inwardly toward said grooved surface portion of said one member to at least partially define said pockets.
 15. A torque-transmitting device as set forth in claim 14 wherein said exhaust openings are formed in said housing at locations intermediate said baffles and said pockets at circumferentially spaced locations around said one member.
 16. An electromagnetic torque-transmitting device comprising rotatable input and output members, an electrical coil associated with said input and output members and energizable to create a magnetic field traversing said members so that relative rotation of said members generates heat and effects transmission therebetween, housing means at least partially enclosing said input and output members and defining a chamber for receiving Cooling medium for dissipating at least in part the heat generated by the transmission of torque between the input and output members, and means for providing a flow of the cooling medium into said housing means and providing pressurized cooling medium therein in a heat-transferring relationship with said input and output members whereby the pressurized cooling medium effects efficient transfer of heat from said members, said housing means including baffle means for directing the cooling medium to impinge against said one member at a plurality of circumferentially spaced locations.
 17. A torque-transmitting device as set forth in claim 16 wherein said one member has an outer surface defining a plurality of grooves which extend in a direction transverse to the axis of rotation of said one member to receive the cooling medium and facilitate a transfer of heat to the cooling medium.
 18. A torque-transmitting device as defined in claim 1 wherein said second member includes a plurality of grooves therein which extend in a direction transverse to the axis of rotation of said second member, said centrifugal force established upon rotation of said second member acting to direct said cooling medium from said grooves and tending to establish a vacuum in said grooves, said means for providing a flow of pressurized cooling medium providing said flow at a pressure which is greater than the pressure established by said centrifugal force to thereby effect the flow of the cooling medium into said grooves. 